Gangcai Liu

Assessment of regional ecological security based on ecological footprint and influential factors analysis: a case study of Chongqing Municipality, China

In recent years, it has been important to objectively evaluate the degree of regional ecological security with regard to resource depletion and to analyse influential factors to assess sustainable development. This paper tries to assess ecological security in Chongqing while investigating the main influencing factors. Calculations of the consumption footprint, production footprint and ecological capacity for Chongqing from 1996 to 2007 based on an ecological footprint approach were carried out. An ecological security index was also calculated from these results and factors influencing security were analysed using factor analysis. Both the consumption and production footprints present an upward trend, contrary to the gradually decreasing trend of ecological capacity. In addition, the ecological security index shows that Chongqing has deteriorated from a level of less risk to that of risk. Factor analysis suggests that the deterioration of ecological security could primarily be ascribed to socio-economic factors and industrialisation. With socio-economic development and industrialisation, appropriate measures must be taken to improve the ecosystem in Chongqing so as to achieve sustainable development. The limitations of the methodology are also discussed and areas that require further research are presented.

Laboratory Investigation of Disintegration Characteristics of Purple Mudstone under Different Hydrothermal Conditions

Disintegration of rock is one of the primary processes of soil formation and geomorphology and is affected considerably by water and heat. This study focused on the disintegration characteristics under laboratory conditions of typical purple mudstone from the Tuodian group of Jurassic red beds (J3t) in Tuodian Town, Shuangbai county, Yunnan Province of southern China. The fresh mudstone was subjected to alternating applications of water, heat and hydrothermal interaction during five treatments: wetting-drying (WD), saturation (ST), refrigeration-heating (RH), a combination of wettingdrying and refrigeration-heating (WDRH), and a combination of saturation and refrigeration-heating (STRH). Each treatment was run in twenty-four cycles. The results showed that there are three types of disintegration: collapsing disintegration, exfoliation disintegration and imperceptible disintegration. The cumulative disintegration rate (percentage of cumulative disintegrated mass to the initiative sample mass passed through a 2 mm sieve) produced a ‘S’-shape function when related to treatment cycle time and closely fit a logistic model (R2 > 0.99). The rank order of the cumulative disintegration rate resulting from the five treatments was as the following: WDRH > STRH > ST > WD > RH. Because of alternating periods of moisture and dryness, WD caused the most disintegration, while RH alone resulted in imperceptible disintegration. Additionally, there was a negative correlation between the disintegration rate of each treatment cycle (percentage of disintegrated mass to the treated sample mass) and treatment cycle number. There was a positive correlation between this rate and temperature change under moist conditions, indicating that a change in temperature greatly accelerates the disintegration of parent rock when water was supplied.

Plants adapted to nutrient limitation allocate less biomass into stems in an arid‐hot grassland

Biomass allocation can exert a great influence on plant resource acquisition and nutrient use. However, the role of biomass allocation strategies in shaping plant community composition under nutrient limitations remains poorly addressed. We hypothesized that species-specific allocation strategies can affect plant adaptation to nutrient limitations, resulting in species turnover and changes in community-level biomass allocations across nutrient gradients. In this study, we measured species abundance and the concentrations of nitrogen and phosphorus in leaves and soil nutrients in an arid-hot grassland. We quantified species-specific allocation parameters for stems vs leaves based on allometric scaling relationships. Species-specific stem vs leaf allocation parameters were weighted with species abundances to calculate the community-weighted means driven by species turnover. We found that the community-weighted means of biomass allocation parameters were significantly related to the soil nutrient gradient as well as to leaf stoichiometry, indicating that species-specific allocation strategies can affect plant adaptation to nutrient limitations in the studied grassland. Species that allocate less to stems than leaves tend to dominate nutrient-limited environments. The results support the hypothesis that species-specific allocations affect plant adaptation to nutrient limitations. The allocation trade-off between stems and leaves has the potential to greatly affect plant distribution across nutrient gradients.

Morphology and controlling factors of the longitudinal profile of gullies in the Yuanmou dry-hot valley

The morphology of the gully longitudinal profile (GLP) is an important topographic index of the gully bottom associated with the evolution of the gullies. This index can be used to predict the development trend and evaluate the eroded volumes and soil losses by gullying. To depict the morphology of GLP and understand its controlling factors, the Global Positioning System Real-time Kinematic (GPS RTK) and the total station were used to measure the detail points along the gully bottom of 122 gullies at six sites of the Yuanmou dry-hot Valley. Then, nine parameters including length (Lt), horizontal distance (Dh), height (H), vertical erosional area (A), vertical curvature (Cv), concavity (Ca), average gradient (Ga), gully length-gradient index (GL), normalized gully length-gradient index (Ngl), were calculated and mapped using CASS, Excel and SPSS. The results showed that this study area is dominated by slightly concave and medium gradient GLPs, and the lithology of most gullies is sandstone and siltstone. Although different types of GLPs appear at different sites, all parameters present a positively skewed distribution. There are relatively strong correlations between several parameters: namely Lt and H, Dh and H, Lt and A, Dh and A, H and GL. Most GLPs, except three, have a best fit of exponential functions with quasistraight shapes. Soil properties, vegetation coverage, piping erosion and topography are important factors to affect the GLP morphology. This study provides useful insight into the knowledge of GLP morphology and its influential factors that are of critical importance to prevent and control gully erosion.

Determination of purple soil loss tolerance based on soil productivity in southwest China

Soil loss tolerance (the T value) is generally defined as the maximum acceptable soil loss that allows a high level of productivity to be maintained for a long period while considering the soil fertility and productivity. The T value is both the basic criterion for determining whether erosion control measures are necessary to conserve the soil and the index used to classify the degree of soil erosion. Therefore, soil loss tolerance must be determined scientifically and rationally. In this study, the ultimate objective was to determine the T value that could sustainably satisfy the needs of local development with regard to regional social progress based on the productivity of the soil. Artificially established plots with soil depths of 10, 20, 40 and 60 cm (4, 8, 16, and 24 in), representing 50, 40, 20 and 0 cm (20, 16, 8, and 0 in) of eroded soil depth, respectively, were used to determine quantitatively the effect of soil erosion on soil productivity. The crops planted within the plots were corn (Zea mays L.) and wheat (Triticum aestivum L.) for summer and winter, respectively, and their yields were used as the proxy measure of the productivity of the soil. The T value was determined by the permissible reduction rate of soil productivity that satisfies the requirements of local sustainable development in the long term and the relationship between the eroded soil depth and soil productivity. The results demonstrated that the crop yield decreased at an exponential rate with an eroded soil depth: with a 1% reduction in crop yield, the soils planted with corn were eroded by 0.92 cm (0.36 in), and those planted with wheat were eroded by 0.94 cm (0.37 in). After analyzing the increase in the local soil productivity and the requirements for sustainable social development, the soil productivity reduction tolerance was found to be 0.1%, and the T value of the studied region was determined to be 11 Mg ha−1 y−1 (4.91 tn ac−1 yr−1).

Temperature and soil microorganisms interact to affect Dodonaea viscosa growth on mountainsides

There is considerable interest in understanding the drivers of plant growth in the context of climate change. Soil microorganisms play an important role in affecting plant growth and functional traits. However, the role of interaction between soil microbes and temperature in affecting plant growth and functional traits remains unclear. The objective of this research was to investigate the effects of soil microbes, temperature, and their interaction on the growth and functional traits of Dodonaea viscosa in a mountain in Yuanmou county, southwest China. The experiment was conducted in climate chambers with a factorial design of three soil microbial communities (inoculated rhizosphere microbes from high elevation, inoculated rhizosphere microbes from low elevation, and autoclaved control) and two temperature conditions (colder and warmer). D. viscosa planted in inoculated rhizosphere microbes from both high and low elevations produced more total biomass with a lower root–shoot allometric exponent, and accumulated significantly more N and P nutrients than those in an autoclaved control, with no significant differences between the two microbial inoculations. Thus, rhizosphere soil microorganisms had positive effects on D. viscosa growth. However, the effect of the microbes on plant growth strongly depended on temperature. Warming had a positive effect on D. viscosa growth in inoculated rhizosphere microbe treatments, while the positive effect disappeared in the autoclaved control treatment. Our results indicate that temperature and soil microorganisms interact to affect D. viscosa growth. As the climate changes in the future in the studied region, the growth of D. viscosa may be greatly affected both directly and indirectly through the temperature–soil microbe interaction.

Modeling the morphology of gully cross sections in the Yuanmou Dry-hot Valley

Abstract Characterizing gully cross sections (GCs) is essential for calculating the volume and erosion rate of the gully. However, little research has focused on modeling the morphology of GCs. This study investigated 456 GCs with a laser distance meter located at the mouth, middle, and head of 152 gullies in the Yuanmou Dry-hot Valley of China; mapped them with AutoCAD software; fitted them with 2nd–6th degree polynomial functions, and discussed the correlation between the coefficients and the morphology of GCs. The results showed that: (1) using a 2nd-degree polynomial function (y = ax2 + bx + c) to describe the morphology of GCs produced a better result than other polynomial functions; (2) the coefficient a of 2nd-degree polynomial function was correlated with depth (r = −0.226, p < 0.01), gradient (r = 0.545, p < 0.01), and activities; and (3) the symmetry axis (−b/2a) of 2nd-degree polynomial function increased with gully change from left-deflection to right-skewed, and the absolute value showed the asymmetrical degree (r = 0.216, p < 0.01). This study will not only help to understand the morphology and evolution of gullies, but will also provide a scientific basis for prevention of gully erosion.

Spatiotemporal variation of soil organic carbon in the cultivated soil layer of dry land in the South-Western Yunnan Plateau, China

The dynamics of soil organic carbon (SOC) in cropland is one of the central issues related to both soil fertility and environmental safety. However, little information is available at county level regarding the spatiotemporal variability of SOC in the southwestern mountainous region of China. Thus, this study aimed to explore spatiotemporal changes of SOC in the cultivated soil layer of dry land in Mojiang County, Yunnan Province, China. Data were obtained from the second national soil survey (SNSS) of 1985 and soil tests for fertilizer application carried out by the Mojiang Agricultural Bureau in 2006. The ANOVA test was applied to determine any significant differences between the datasets, while semivariogram analysis was performed on geostatistics via an ordinary Kriging method in order to map spatial patterns of soil organic carbon density (SOCD). The results revealed that SOCD in the cultivated soil layer significantly decreased from 3.93 kg m-2 in 1985 to 2.89 kg m-2 in 2006, with a total soil organic carbon stock (SOCS) decrease of 41.54×104 t over the same period. SOCS levels fell most markedly in yellow-brown soil at a rate of 51.52%, while an increase of 8.70% was found in the analysed latosol. Geostatistical analysis also showed that the recorded changes in SOCD between 1985 and 2006 were spatially structured. The decreasing trend might be attributed to the combined action of intense cultivation, major crop residue removal without any protective tillage measures, unreasonable fertilization and natural climatic diversity inducing a large decrease in SOC in the studied cultivated dry land region of Mojiang County. Therefore, management measures such as protective tillage should be undertaken in order to enhance soil C sequestration.

Rainfall Interception in Two Contrasting Forest Types in the Mount Gongga Area of Eastern Tibet, China

An important component of the water cycle in ecological systems, rainfall interception by virgin forests was here calculated from gross precipitation minus through fall and stem flow. The through fall measurement system was designed on the basis of a 3 m long trough mounted beneath the canopy and able to operate successfully under a range of rainfall conditions. Stem flow was measured using spiral collars consisting of a split plastic hose attached to sampled trees, with gross precipitation measured in an open area via a tipping-bucket rain gauge. This study was carried out to evaluate rainfall interception and distribution patterns of gross precipitation in two contrasting rainforest types (coniferous and broadleaved/coniferous mixed) in the Mount Gongga area on the eastern fringe of Tibet, China, from 2008 to 2009. Net precipitation was found to be primarily composed of through fall, while stem flow contributed less than 0.5% (0.1% and 0.4% in conifer and mixed forest, respectively) to total gross precipitation (GP) and was thus negligible in both forest types. The difference in the interception loss fraction between conifer and mixed forest was greater than 30%, with the interception loss of the former apparently more than that of the latter mainly due to the increased presence of small droplets produced by coniferous leaves. Additionally, interception loss in conifer forest was more dependent on rainfall than that in mixed forest. In contrast, through fall and stem flow exhibited the opposite pattern, likely attributable to a through fall lag of 8 to 10 h after rainfall in mixed forest but not in conifer forest.

Notice of Retraction Degradation degree assessment on the ecosystem of Yuanmou Dry-hot Valley

Take the Yuanmou Dry-hot Valley as an example, this paper puts forward the concept, index system and evaluation methods of ecosystem degradation degree, which will promote the theory and practices of ecological restoration.